Wind-power windmills are known to kill birds, particularly raptors and bats. The birds are killed when they fly into the path of the windmill blades. As an indication of the violence of some of these incidents, many of the birds suffer decapitation or instant and usually fatal loss of one or more wings or body portions. Although windmills are responsible for a tiny, tiny fraction of the total accidental bird-kills due to man (<<1%), most of which are due to vehicles and building structures, those killed by windmills have garnered virtually all the attention as they are so visible and they ironically happen while trying to do something environmentally favorable, i.e., generate wind power.
A search of the wind turbine prior art reveals that most inventors in this field have tried to solve the problem by moving away from large exposed two and three blade windmills to windmills that are generally a lot smaller and have a variety of protective or air-funneling shrouds through which air passes but birds cannot, at least not easily. The trouble with these is that they generally are not as efficient as the existing large two and three bladed windmills such as the 5000 units at Altamont Pass in California. The suggested systems are indeed much more bird-safe but many, and perhaps all of them, are not as efficient as the current bird-dangerous large systems. Evidence of this simple fact is that the industry continues to build the current design in ever-larger numbers despite these alternative inventive designs being known. This is not to say smaller units are of no use; in fact, they may be ideal for home installations, for example.
I found two wind power patents which tried to address the bird-kill issue even for the existing base of large bare-bladed commercial power-generation windmills. These are as follows:
U.S. Pat. No. 6,623,243 to Hodos; “MINIMIZATION OF MOTION SMEAR—AN APPROACH TO REDUCING AVIAN COLLISIONS WITH WIND TURBINES”. Hodos teaches that the visual image smearing of the rotor blades can be lessened or alleviated by painting a variety of optical patterns on one or more of the rotating turbine blades. The present inventor understands that this approach has been, or is being, tried at Altamont Pass, Calif. but I am not aware of any published results. Many raptors (hawks, eagles, etc.) are killed while diving near the ground to catch rodents. It is thought by some that during this attack-phase at low altitude, the raptor is not paying attention to anything but the rodent, seemingly a reasonable assumption. This would seem not to bode well for the hope that the bird or raptor will be noticing (better) the painted or patterned blades. Further, and certainly less important, depending on the pattern and colors, humans might find such visual colorations and patternations disagreeable. It is also not clear how well such a visual strategy can work at night.
US 2005/0162978 A1 to Lima, “METHOD OF INCREASING AVIAN SAFETY IN AND AROUND WIND POWERED ELECTRICITY PRODUCTION FACILITIES”. Lima utilizes ultrasonic sounds to drive away the birds. Once driven away, motion detection sensors allow the ultrasonic speakers or annunciators to remain off until another bird is motion-detected. In that manner, the birds do not become conditioned to an always-on sound. The present inventor is not aware of such a system being tried. Some concerns regarding the reliability and efficacy of such a system are 1) motion detectors have a lot of false alarms due to moving branches, grass, etc., and some approaches such as video-motion detection can be confused or blocked by weather, 2) other windmills will generate a lot of motion signals which would need to be discounted, 3) the ultrasonic signal may also be irritating to other natural life such as rodents and insects, and maybe even humans, 4) the ultrasonic signals may be injurious or harmful to bird hearing if they are loud enough to be irritating, 5) birds flying into the area, such as on a migration journey, will represent significant daily numbers of “untrained” birds, so the ultrasonics may have to be on all or most of the time, thereby teaching resident birds there is nothing to be afraid of.
In any event, both of the above patents/apps are competent and well intentioned proposed solutions. They both are argued to act to avoid collisions which would seem to be the logical first choice over trying to ameliorate the severity of collisions.